It is known as for example from the M. L. Benjamin et al U.S. Pat. Nos. 3,171,145 and 3,214,773 to axially slidably key a tap holder in a housing for yieldable relative axial movement while torque is transmitted from the housing to the tap holder. Keying arrangements as disclosed in these patents under high torque loads entails either substantial sliding friction between the keys and the keyways or high fricton rubbing contact of the side of the shank of the tap holder with the guide bore of the housing socket.
In order to decrease frictional resistance to relative axial movement of a tap holder with respect to a housing it has been proposed as in the Bilz U.S. Pat. No. 3,091,473 to employ torque transmitting balls in axially extending grooves of the tap holder and housing. However, in such construction relative axial movement of the tap holder and housing may entail skidding of the balls and even a minute variation in the angular spacing of the grooves may result in the condition wherein the entire torque load is imposed on a single ball with attendant shifting of the shank of the tap holder into high friction rubbing contact with the bore of the housing during relative axial movement of the tap holder and housing.